The background description provided herein is for the purpose of generally presenting the context of the present invention. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions. Work of the presently named inventors, to the extent it is described in the background of the invention section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
A cochlear implant (CI) is a device that restores hearing by directly stimulating the auditory nerve using an electrode array that is surgically placed in the cochlea. The CI device includes a sound processor component, typically worn behind the ear, which processes and converts sounds detected by a microphone into electrical signals sent to implanted electrodes. The CI sound processor is programmed by an audiologist who determines a number of processor programming parameters that specify the electrical signals sent to implanted electrodes to attempt to optimize hearing outcome. The number of electrodes in a CI electrode array range from 12 to 22, depending on the manufacturer.
We recently developed and are currently testing image-guided cochlear implant programming (IGCIP) strategies that rely on patient-specific knowledge of spatial relationship between implanted electrodes and inner ear structures. The inner ear structures-of-interest (SOIs) are the scala tympani (ST), the scala vestibuli (SV), and the spiral ganglion (SG). The ST and the SV are the two principal cavities of the cochlea. The SG is an anatomical region that contains the group of nerves targeted for stimulation by implanted electrodes. FIG. 1A shows surfaces of the ST, the SV and the SG of a representative subject. FIG. 1B shows an example surface model of an electrode array inserted into the cochlea, and FIG. 1C shows a surface of the active region (AR), which is the interface between the SG and the union of the ST and the SV. The AR is the region of nerves most likely to receive electrical stimulation from implanted electrodes.
The IGCIP strategies are enabled by a number of algorithms we have developed that permit determining the position of implanted electrodes relative to the SOIs using a pre- and a post-implantation CT [2-7]. In a preliminary study with over thirty CI recipients, we have shown that IGCIP strategies can significantly improve hearing outcomes [1]. One issue with the IGCIP strategies is that it does not extend to CI recipients for whom a pre-implantation CT is not available. This is because implant related image artifacts present in post-implantation CTs make it difficult to localize the SOIs in those images directly. Thus far, the SOIs have been first localized in a pre-implantation CT and then mapped onto a post-implantation CT, on which their positions relative to implanted electrodes are analyzed. Specifically, this approach, which we previously developed, includes three steps. First, we segment the SOIs in a pre-implantation CT. Next, we localize the electrodes in a corresponding post-implantation CT. Finally, we rigidly register the two CTs to determine the position of implanted electrodes relative to the SOIs. When subjects receive unilateral CIs, we have also developed approaches for determining electrodes position relative to SOIs using post-implantation CTs alone, without requiring a corresponding pre-implantation CT. This approach involves segmenting the SOIs in the implanted ear by mapping the SOI surfaces segmented from the contralateral normal ear [8, 14]. However, the approaches we developed so far cannot be used for many CI recipients for whom a pre-implantation CT of neither ear is available.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.